Phonon wave-packet dynamics at semiconductor interfaces by molecular-dynamics simulation

We directly observe phonon wave packets of well-defined frequency and polarization scattering at a coherent semiconductor interface using molecular-dynamics simulations. We find that in the low-frequency limit the transmission coefficients of both longitudinal and transverse acoustic phonons agree well with those predicted by the continuum-level based acoustic mismatch model. However, the transmission coefficients rapidly decrease close to the cutoff frequency, a result that can be understood within a simple one-dimensional discrete atomic-chain model. We also find that the transmission coefficient for transverse acoustic phonons depends strongly on the relative orientation of the polarization and the Si-Si bonds in the diamond lattice structure. (C) 2002 American Institute of Physics.